June 19, 2012

RSA HE2 in progress

This is a 2 way passive speaker that I'm developing, featuring a high sensitivity pro 10" midwoofer and a waveguide loaded compression driver. Due to the high sensitivity, it will work well for valve amps and also home theatre use. It features 94 dB sensitivity with an 8 ohm load and 50 Hz bass extension. A careful balance of bass extension, box size and sensitivity has been chosen. Higher sensitivity requires more or bigger mid drivers, or giving up bass extension which makes a subwoofer necessary. The box is ply and will have a clear finish.

Ply cut the old fashioned way:

Pieces on the left are for a shelf port. Very generously sized with flaring on both ends (not yet shown). A front port was chosen for flexibility, avoiding the need for feet with downfiring, or making offset from the rear wall critical.

10" waveguide with 10" midwoofer:

Bracing:

A groove has been cut where butt joins have been used. This groove is painted black to give a nice fine line.

After paint applied to grooves:

It looks like this:

Box damping with a mix of screenings as an aggregate with bitumin rubber. It's quite expensive, but very effective and also provides the benefit of sealing up the box. In the actual box I've used a fine aggregate with 7mm screenings and it looks very much like a bitumin road. However, it has some flexibility which is desired since the intended result is not simply a heavier box but one that is dead and well damped.

Priming of the box interior prior to applying bitumin rubber damping:

Upside down with vent shown on top:

Baffle not yet attached. Damping applied. I have since applied more along with the screenings, but around four applications are required.

7 comments:

The dual woofer version requires either a sealed box or a bigger box. The sealed version suits HT well where extension to meet a sub is required. A vented version to still get down to 50 Hz would require a taller, deeper, wider box, basically twice the volume!